Dry-cow treatment cures about 40 percent to 60 percent of cows infected with major mastitis pathogens at dry off, says Ynte Schukken, veterinarian at Cornell University.

Schukken summarized several factors which impact the cure rate of dry-treated cows at the National Mastitis Council's annual meeting held in Reno, Nev., in February. Understanding how these criteria influence cure rates can help you fine-tune the use of dry-cow antibiotics in your herd. Here are some of the factors outlined by Schukken and their influence on cure rates:

  • Age of the cow. Older cows tend to have a lower probability of cure compared to first-lactation animals.
  • Somatic cell count before dry off. Cows with higher cell counts before dry-off were less likely to be cured.
  • Number of quarters infected. Cows with more than one quarter infected were less likely to be cured.
  • Antibiotic susceptibility. If a cow is infected with penicillin-resistant Staph. aureus mastitis, her cure rate is substantially lowered.
  • Choice of antibiotics. Proper choice of antibiotics tends to influence cure rate.
  • Combination of treatments. Antibiotic treatment combined with parenteral or intravenous therapy has been shown to have a beneficial effect on cure rates.